Composite ceramic articles

ABSTRACT

Dense monolithic bodies having complex internal cavities or passageways are made from sinterable powders by mixing the sinterable powders with an organic film-forming resin, forming a tape from the resin, cutting or stamping a multiplicity of disks, plates or chips from the tape which have the peripheral dimensions of the object to be made, stamping or cutting holes in the disks according to a predetermined pattern, laminating the disks to provide an object with the desired internal structure, and finally heat treating to remove the resin binder and sintering the powdered particles together to form a monolithic structure.

11] 3,725,186 14 1 Apr. 3, 1973 1541 COMPOSITE CERAMIC ARTICLES 75Inventor: John F. Lynch, Oak Ridge, NJ.

[73] Assignee: National Beryllia Corp., Haskell,

[22] Filed: Nov. 25, 1970 [21] Appl. No.: 92,775

52 u.s.c1. ..161/l09, 156/89, 264/58, 264/60 51 1111. (:1 .3321,3/10,C04b 39/00 [58] Field of Search ..161/109, 113, 112; 264/241,264/57, 59, 60, 61, 62, 67; 156/89, 155; 75/200; 29/1822, 182.5

[56] References Cited UNITED STATES PATENTS 3,150,974 9/1964 Lund et a1...75/208 3,192,086 6/1965 Gyurk ....159/89 3,226,456 12/1965 Ryshewitchet a1. ..264/60 3,235,939 2/1966 Rodriguez et al.... .....156/89 UX3,239,323 3/1966 Folweiler .....l56/89 UX I H I ljj' l l 11-2 l I 3 I! I3,436,307 4/1969 Johnson etal ..29/l82.2 X 3,436,451 4/1969 Wasser..264/61 X 3,502,520 3/1970 Schwartz ..264/63 X 3,518,756 7/1970 Bennettet al. ..264/6l X 7 3,564,328 2/1971 Bagley .....264/57 x PrimaryExaminer-Robert F. Burnett Assistant Examiner-Joseph C. GilAttorney-Greene 8t Durr [57] ABSTRACT Dense monolithic bodies having;complex internal cavities or passageways are made from sinterablepowders by mixing the sinterable powders with an organic film-formingresin, forming a tape from the resin, cutting or stamping a multiplicityof disks, plates or chips from the tape which have the peripheraldimensions of the object to be made, stamping or cutting holes in thedisks according to a predetermined pattern, laminating the disks toprovide an object with the desired internal structure, and finally heattreating to remove the resin binder and sintering the powdered particlestogether to form a monolithic structure.

3 Claims, 5 Drawing Figures 7 'PATENIEn/m I975 3,

INVENTOR F|G 2 John E Lynch ATTORNEYS COMPOSITE CERAMIC ARTICLES Thisinvention relates to a process of making dense monolithic bodies withcomplex internal cavities or passages from sinterable powders and to theproduct thus obtained.

Most industrial and technical ceramic or metal articles can be made withcomplex external geometries, but not with complex internal cavities orpassages. Some ceramic casting molds have been made by the lost-wax typeof process, but such molds are thinwalled and not adapted for repeated,heavy industrial .USB.

Among the objects of the invention is to provide a rugged, monolithicproduct formed of a sinterable material, said product having a complexinternal cavity or passage of substantially any desired geometry. Theinternal cavity or passage may include under cut portions and complexportions in the form of rings, pockets, channels, baffles, deflectors,gratings, etc. Such articles, especially when made of ceramics, areuseful as mixing and/or heat exchange passages for molten compositions.Ceramic articles with internal cavities or passageways ending in square,polygonal or irregular outlet holes can also be produced by the process.

The objects of the invention are attained by providing a tape ofresin-bonded, but unsintered ceramic, metal or other sinterableparticles, cutting a series of disks or plates from the tape which havethe shape of the exterior of the device to be produced,'punching holesor cutting out the interior of said disks or plates in a predeterminedway so as to provide the complex internal passage or cavity when thedisks or plates are stacked or laminated, preliminarily molding saidstacked plates and finally firing the laminated structure to provide themonolithic ceramic desired.

Processes are known for the manufacture of resinbonded ceramic particlestogether. Such a process is shown, for example, in U.S. Pat. No.2,966,719 or in British Pat. No. 1,100,756. According to such processes,the finely ground ceramic powder is mixed with about 2.5 to 30 percentof a resin forming composition, spread onto a moving belt or film, driedand/or heat treated to further polymerize or solidify the resin andstriped from the belt. The tape or film produced by such process can be0.003 to 0.060 inches thick and any desirable width. The tape can bereadily cut to shape, punched or otherwise formed and, when fired, theresin binder is eliminated, preferably before firing at the finalsintering temperature.

Any type of ceramic, metal or other sinterable particles can be mixedwith the resin binder to form the unfired tape. Ceramic particles whichare useful with the invention include thoria, alumina, ytteria, variouskinds of ferrites, beryllia, zirconia, nitrides, borides, carbides,titanates, various mixtures of such ceramics, etc. The several disks orplates which are laminated to make the final product may be identical incomposition or may be made of different powdered ceramic products.Generally, the ceramic oxide or composition which forms the basis forthe final product is 70 to 99.97 percent pure. Thus, it is possible tomake a product of very high purity. Similarly particles of any metal oralloy or other sinterable inorganic-material can be formed into a tapeand finally molded in the same way.

In the accompanying drawing, which illustrates, by way of example, aconstructional form of the invention,

FIG. 1 is a view of a green or unsintered tape consisting mainly ofinorganic particles bonded by a synthetic resin composition illustratinghow disks may be cut therefrom.

FIG. 2 is an exploded view of a series of disks, such as obtained fromthe tape of FIG. 1 but showing how the disks may be punched out, cut toform an object such as shown in FIG. 3.

FIG. 3 is a cross-sectional view of a laminated set of disks prior tosintering, said disks being assembled to form a heat exchange devicewith a complex. internal labyrinth with an intricate series of passagesso as to 'avoid laminar flow of the material therethru.

FIGS. 4 and 5 show how two disks can be combined to form an articlecontaining a passageway and having an orifice with a diamond shapedopening.

As stated above, the disks or tape, from which the disks are cut, isgenerally about 0.003 to 0.060 inches thick, so that the thickness ofthe layers shown in FIG. 3 may be considered as somewhat exaggerated, oron the other hand, the entire device may be considered as greatlymagnified. One advantage of the present invention is that products withrelatively small outlets can be made.

A plurality of disks 11 are cut from the tape 10. Each one of a seriesof disks is then further processed by forming the portion of thelabyrinth therein which it is to surround in the finished product. Thus,the disk 11-1 has the circular opening 12 cut out, the disk 11-2 has apair of small holes 13 and 14 punched therein, the disk 11-3 has theelliptical opening 15 formed therein and disk 12-4 has the outletorifice 16 formedtherein. Instead of one disk 11-1, 11-2, etc. two ormore of each of such disks can be employed in the stack of FIG. 3 toprovide the exact internal outline of the labyrinth desired.

The stack of disks is preliminarily pressed at about to 1,000 pounds persquare inch while maintained at a temperature of about 25 to C.Thereafter, the composite laminate is fired in a two-step process, toexpel the resin binder and then to sinter the ceramic grains. In thecase of a device such as illustrated in FIG. 3 in which the powderedinorganic material is BeO of 96 to 99.95 percent purity, the preliminaryheating to remove the binder occurs below 600 C and the product is thenfired at about 1,400 to l,600 C for l to 4 hours to sinter the BeO.

In the product shown in FIGS. 4 and 5, two similar disks 11-5, havingslotted opening 17 punched therein, can be combined in such a manner asto provide a diamond shaped opening 18 with sharp edges.

In the finished object, the laminations are completely sintered into amonolithic structure with all joints between laminations hermeticallysealed. However, close examination, especially at the edges and in theinteriorcavity or cavities, will reveal the lines or projectionscorresponding to the interfaces between the laminations.

I claim:

1. As an article of manufacture, a sintered monolithic, inorganicceramic body, comprising a plurality of stacked laminations ofapproximately equal thickness, each of a series of said laminationsextending from one side of the body containing at least one interiorpassageway connecting with at least one passageway in the adjacentlaminations of said series, at least one of said interior -laminationsof said series having a passageway which is undercut with respect to atleast one of the passageways in adjacent laminations.

2. The article as claimed in claim 1 in which the ceramic consistsessentially of beryllium oxide. 5

3. The article as claimed in claim 1 in which the inorganic ceramicmaterial is a metal oxide.

2. The article as claimed in claim 1 in which the ceramic consists essentially of beryllium oxide.
 3. The article as claimed in claim 1 in which the inorganic ceramic material is a metal oxide. 